Emerging Frontiers in Photoacoustic Spectroscopy Detection

A special issue of Photonics (ISSN 2304-6732).

Deadline for manuscript submissions: closed (20 September 2023) | Viewed by 9085

Special Issue Editor

The National Institute of Optics, Florence, Italy
Interests: photoacoustic spectroscopy; cavity-enhanced spectroscopy; ultrasensitive gas sensing

Special Issue Information

Dear Colleagues,

The market of gas sensors has been booming in recent years, especially under the global background of carbon emission reduction. Gas sensors with high sensitivity, high selectivity, fast response, low cost, and a small footprint are desirable across a broad range of applications in environment, energy, safety, and public health. Photoacoustic spectroscopy (PAS) is a promising candidate technique which relies on the detection of acoustic waves generated by periodic local heating and thermal expansion in the vibration–translation (V–T) relaxation process of excited molecules after absorbing photons. PAS signals linearly increase with laser power, rather than a long absorption path. The use of acoustic transducers instead of photodetectors makes PAS sensors more compatible with various laser wavelengths, as sensitive photodetectors are not always available over a wide wavelength range. Therefore, PAS sensors have the unique features of a low cost and compact size. In addition, gas sensors with ultra-high sensitivity of parts-per-trillion or even parts-per-quadrillion have been emerging to provide alternatives to expensive and bulky metrology instruments for science investigation and specific applications. The purpose of this Special Issue is to highlight the progress of gas sensor development based on novel laser sources, new acoustic transducers, advanced photoacoustic spectroscopic methods, and combinations with efficient signal processing algorithms such as deep learning. In addition, PAS gas sensors developed for various applications, including medical analysis, environmental monitoring, and so on, are also welcome.

Dr. Zhen Wang
Guest Editor

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Keywords

  • gas sensors
  • novel laser sources
  • new acoustic transducers
  • advanced photoacoustic spectroscopic methods
  • medical analysis
  • environmental monitoring

Published Papers (5 papers)

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Research

11 pages, 640 KiB  
Article
Mach–Zehnder Modulator Output in Time and Frequency Domain—Calculation and Experimental Confirmation
by Sander Vervoort, Yannick Saalberg and Marcus Wolff
Photonics 2023, 10(3), 337; https://doi.org/10.3390/photonics10030337 - 21 Mar 2023
Cited by 1 | Viewed by 2601
Abstract
The Mach–Zehnder intensity Modulator (MZM), named after Ludwig Mach and Ludwig Zehnder, is based on the corresponding interferometer. It splits light into two counter-rotating partial beams, which are later recombined with a controlled phase difference. The output of the MZM depends on the [...] Read more.
The Mach–Zehnder intensity Modulator (MZM), named after Ludwig Mach and Ludwig Zehnder, is based on the corresponding interferometer. It splits light into two counter-rotating partial beams, which are later recombined with a controlled phase difference. The output of the MZM depends on the phase difference of the interferometer paths. This phase difference is usually adjusted by an electrical voltage applied to a Phase Shifter (PS) placed in one of the interferometer arms. For MZM applications in which the wavelength is changing, the applied voltage must be adjusted accordingly. We derived the equations describing the MZM output in the frequency domain for the case of a triangular PS voltage (necessary for a sinusoidal output) and compared the analytical results with measurements. Our setup uses an Optical Parametric Oscillator (OPO) with a tunable wavelength from 3.2–3.5 μm as the light source and a Lithium Tantalate (LT)-PS for the MZM’s phase modulation. The novel insights enable new control methods for MZMs particularly suited for spectroscopic applications where the wavelength is scanned or otherwise altered. Full article
(This article belongs to the Special Issue Emerging Frontiers in Photoacoustic Spectroscopy Detection)
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9 pages, 2664 KiB  
Communication
Simultaneous Detection of Gas Concentration and Light Intensity Based on Dual-Quartz-Enhanced Photoacoustic-Photothermal Spectroscopy
by Hao Liu, Xiang Chen, Lu Yao, Zhenyu Xu, Mai Hu and Ruifeng Kan
Photonics 2023, 10(2), 165; https://doi.org/10.3390/photonics10020165 - 04 Feb 2023
Viewed by 1153
Abstract
This research proposes a method for the simultaneous acquisition of the second harmonic (2f) signal of quartz-enhanced photoacoustic spectroscopy (QEPAS) and the first harmonic (1f) signal of quartz-enhanced photothermal spectroscopy (QEPTS) based on the dual-quartz-enhanced photoacoustic–photothermal spectroscopy. The laser [...] Read more.
This research proposes a method for the simultaneous acquisition of the second harmonic (2f) signal of quartz-enhanced photoacoustic spectroscopy (QEPAS) and the first harmonic (1f) signal of quartz-enhanced photothermal spectroscopy (QEPTS) based on the dual-quartz-enhanced photoacoustic–photothermal spectroscopy. The laser beam is first wavelength-modulated by the injection current and then intensity-modulated by an acoustic-optic modulator. The frequency of the wavelength modulation is half of the QTF1 resonant frequency, and the frequency of the intensity modulation is equal to the QTF2 resonant frequency. A modulated laser beam traveled through the two arms of the QTF1 and converged on the root of the QTF2. The 2f photoacoustic and 1f photothermal signals are concurrently obtained using the frequency division multiplexing technology and lock-in amplifiers, which allows the simultaneous detection of the gas concentration and laser light intensity. CH4 is chosen as the target gas, and the variations of the 2f photoacoustic and 1f photothermal signals are evaluated at various gas concentrations and light intensities. According to the experiments, the amplitude of the 1f photothermal signal has a good linear connection with light intensity (R2 = 0.998), which can be utilized to accurately revise the 2f photoacoustic signal while light intensity fluctuates. Over a wide range of concentrations, the normalized 2f photoacoustic signals exhibit an excellent linear response (R2 = 0.996). According to the Allan deviation analysis, the minimum detection limit for CH4 is 0.39 ppm when the integration time is 430 s. Compared with the light intensity correction using a photodetector for the QEPAS system, this approach offers a novel and effective light intensity correction method for concentration measurements employing 2f analysis. It also has the advantages of low cost and compact volume, especially for mid-infrared and terahertz systems. Full article
(This article belongs to the Special Issue Emerging Frontiers in Photoacoustic Spectroscopy Detection)
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10 pages, 3124 KiB  
Communication
Compact and Low-Power-Consumption CO Sensor Using a QCL with Intermittent Scanning Technique
by Qinduan Zhang, Jie Hu, Yubin Wei, Binkai Li, Guancheng Liu, Tingting Zhang, Zhaowei Wang, Weihua Gong and Tongyu Liu
Photonics 2023, 10(1), 95; https://doi.org/10.3390/photonics10010095 - 15 Jan 2023
Viewed by 1482
Abstract
A compact and low-power-consumption gas sensor using a quantum cascade laser (QCL) emitting at 4.6 μm for measurement of carbon monoxide (CO) was proposed and experimentally demonstrated. A compact sensor structure with a physical dimension of 14 × 10 × 6.5 cm3 [...] Read more.
A compact and low-power-consumption gas sensor using a quantum cascade laser (QCL) emitting at 4.6 μm for measurement of carbon monoxide (CO) was proposed and experimentally demonstrated. A compact sensor structure with a physical dimension of 14 × 10 × 6.5 cm3 was designed. A new intermittent scanning technique was used to drive the QCL to reduce the power consumption of the system. In this technique, the power consumption of the sensor is as low as 1.08 W, which is about 75% lower than the conventional direct absorption technology. The stability of the CO sensor was demonstrated by continuously monitoring CO concentration for more than 1 h. In the concentration range of 10 ppm to 500 ppm, the CO sensor exhibited a satisfactory linear response (R-square = 0.9998). With an integration time of 202 s, the minimum detection limit was increased to 4.85 ppb, based on an Allan deviation analysis. Full article
(This article belongs to the Special Issue Emerging Frontiers in Photoacoustic Spectroscopy Detection)
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7 pages, 2133 KiB  
Communication
Mid-Infrared Frequency Modulation Spectroscopy of NO Detection in a Hollow-Core Antiresonant Fiber
by Mengyuan Hu, Andrea Ventura, Juliano Grigoleto Hayashi, Francesco Poletti and Wei Ren
Photonics 2022, 9(12), 935; https://doi.org/10.3390/photonics9120935 - 03 Dec 2022
Viewed by 1226
Abstract
Mid-infrared frequency modulation spectroscopy (FMS) in a tellurite hollow-core antiresonant fiber (HC-ARF) is investigated for gas detection. The spectroscopic system is demonstrated for nitric oxide (NO) detection by exploiting its strong absorption line at 1900.08 cm−1 with a quantum cascade laser (QCL). [...] Read more.
Mid-infrared frequency modulation spectroscopy (FMS) in a tellurite hollow-core antiresonant fiber (HC-ARF) is investigated for gas detection. The spectroscopic system is demonstrated for nitric oxide (NO) detection by exploiting its strong absorption line at 1900.08 cm−1 with a quantum cascade laser (QCL). By modulating the injection current of the QCL at 250 MHz and measuring NO in a 35 cm long HC-ARF, we achieve a noise equivalent concentration of 67 ppb at an averaging time of 0.1 s. Compared to direct absorption spectroscopy with a low-pass filter for etalon noise reduction, the FMS technique shows an improvement factor of 22. The detection limit of FMS can be further improved to 6 ppb at a longer averaging time of 100 s, corresponding to a noise equivalent absorption coefficient of 1.0 × 10−7 cm−1. Full article
(This article belongs to the Special Issue Emerging Frontiers in Photoacoustic Spectroscopy Detection)
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12 pages, 3063 KiB  
Article
All-Fiber Photoacoustic Gas Sensing with Interferometric Location
by Meng Li, Mengpeng Hu, Hui Zhang, Jianing Wang, Tongyu Tang, Mai Hu and Qiang Wang
Photonics 2022, 9(8), 546; https://doi.org/10.3390/photonics9080546 - 03 Aug 2022
Cited by 3 | Viewed by 1853
Abstract
Photoacoustic spectroscopy (PAS) is a promising gas detection technique with high sensitivity, fast response, and good stability. Frequency-modulated continuous-wave (FMCW) interferometry offers precise distance detection with high spatial resolution. The combination of PAS and FMCW may lead to an optical technique for the [...] Read more.
Photoacoustic spectroscopy (PAS) is a promising gas detection technique with high sensitivity, fast response, and good stability. Frequency-modulated continuous-wave (FMCW) interferometry offers precise distance detection with high spatial resolution. The combination of PAS and FMCW may lead to an optical technique for the simultaneous extraction of gas concentration and location information. Herein, we demonstrate this technique in an all-fiber sensing system by blending a fiber-pigtailed PAS sensor with an FMCW interferometer. As an example, we have measured the methane concentration and location by employing time-division multiplexing, showing a minimum detection limit of 28 ppm and a spatial resolution of 3.87 mm over a distance of ~4.9 m. This study enables the realization of a versatile technique for multiparameter gas sensing in gas leakage detection and gas emission monitoring. Full article
(This article belongs to the Special Issue Emerging Frontiers in Photoacoustic Spectroscopy Detection)
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